Leicester Square itself was transformed into a scene from Greek mythology, with Greek soldiers lining the red carpet and ancient relics strewn across the Square’s garden.

Giant flames also roared into the wet night sky, while the soundtrack provided a stirring backdrop to the red carpet events.

The film, which unfolds as a brash 3D epic, is due to open in UK cinemas on April 2 and offers a re-telling of the Greek legend of Perseus, who is forced to defeat the Gods and creatures such as The Medusa and The Kraken, to protect the woman he loves.

Early word has so far been mixed from critics who caught early screenings. US trade publication Variety, for instance, wrote: “Even more haphazardly plotted than the original, Clash of the Titans boasts 3D imagery and kinetic action that can’t obscure a movie that is, finally, pretty flat.

“Influenced almost as much by The Lord of the Rings as a 1981 namesake most notable for Ray Harryhausen’s stop-motion effects, the technical upgrade doesn’t improve the clunky mythological underpinnings, while the script ratchets up the man-vs.-the-gods quotient.

“Result feels mostly like a (very expensive) kids’ pic, and international prospects appear more promising than domestic box office, which, after a muscular opening – with apologies to the gods – should be somewhat less than titanic.”

The Hollywood Reporter was more favourable, however, stating: “After an awkward half-hour or so as it struggles toward a visual style to represent the world of Greek mythology, Clash of the Titans kicks into action with a battle between human warriors and a giant scorpion…”

It adds: “Solid teamwork by a host of digital animators, special effects personnel, art directors, hair, makeup and prosthetic designers and game and athletic actors make Clash a popcorn movie that reaches back to the fantasy epics of old and forward into the digital future, where the word “unimaginable” no longer exists.”